package alg;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


public  class Solution {
        public List<List<Integer>> threeSum(int[] nums) {
            List<List<Integer>> ret = new ArrayList();
            //1.排序
            Arrays.sort(nums);

            //2.利用双指针解决问题
            int n = nums.length;
            for(int i = 0;i< n ;)
            {
                //固定数a
                if(nums[i] >= 0){
                    break;
                }
                int left = i +1,right = n - 1,target = -nums[i];
                while(left < right){
                    int sum = nums[left] + nums[right];
                    if(sum > target){
                        right--;
                    }else if(sum < target){
                        left++;
                    }else{
                        // nums[i]  nums[left] nums[right]
                        ret.add(new ArrayList<Integer>(Arrays.asList(nums[i],nums[left],nums[right])));
                        left++;
                        right--;
                        //去重，left，right
                        while(left < right && nums[left] == nums[left - 1]) left++;
                        while((left < right && nums[right] == nums[right + 1])) right--;
                    }
                }
                //去重；i
                i++;
                while(i < n && nums[i] == nums [i - 1]) i++;
            }
            return ret;
        }


    public static void main(String[] args) {
        Solution alg1 = new Solution();
        int[] arrys = {-1 , 0 , 1 ,2 , -1 ,-4};
        List<List<Integer>> eas = alg1.threeSum(arrys);
        System.out.println(eas);
    }
}
